Standby power source for an ac alarm system

ABSTRACT

A standby power source connected to AC power mains for supplying AC power to an AC alarm system when there is a main power failure comprises a source of DC power, inverter means for converting DC power to AC power and controlled switching means for connecting the source of DC power to the inverter means and for transferring the connection of the AC alarm system from the AC power mains to the inverter means at the time of a power failure.

United States Patent 91 Viger, Jr. 1 July 17, 1973 [54] STANDBY POWERSOURCE FOR AN AC 3,348,060 10/1967 .lamieson 307/66 ALARM SYSTEM3,609,506 9/]97] Frezzolini et al. 307/66 [75] Inventor: geyge P. VIger,Jr., Commack, Primary Examiner Herman J. Hohauser Attorney-Sylvester J.Liddy, Charles E. Baxley [73] Assignee: Signal Communications, Inc.,East et Northport, N.Y.

[22] Filed: Mar. 15, 1972 [57] ABSTRACT [21 1 Appl. No.: 234,906 Astandby power source connected to AC power mains for supplying AC powerto an AC alarm system when [52] U S Cl 307/66 340/276 there is a mainpower failure comprises a source of DC [51] liozj 7/00 power, invertermeans for converting DC power to AC [58] Fie'ld 340/276 power andcontrolled switching'means for connecting the source of DC power to theinverter means and for [56] References Cited transferring the connectionof the AC alarm system UNITED STATES PATENTS Speer 307/66 A. C POWER ISOURCE HEEL INVERTER MEANS TRANSFER CONTROL MEANS BATTERY from the ACpower mains to the inverter means at the time of a power failure.

2 Claims, 3 Drawing Figures A. c ALARM SYSTEM g EE'EEQ mm; Jq1 17,1973 A3,746,878

A c PowE souRcE A c. ALARM sYsTEM TRANSFER CONTROL MEANS FIG. I'

INVERTER MEANS BATTERY r (T to Transfer Conirol TRANSISTOR Means 2 bum",OSCILLATOR 8 1, CIRCUIT Q Q E to neutral line 0 TI T2 to Transfer commINVERTER MEANS 1 F IG. 2

' Means 5 v I5 I T l8 l7 2K2\ 7Q }|nv e r1er AC g f2K3 to Baflery |3 I Mdns Z e l Charger |6 l -/|K3 to Bane -lK2 AC ay 2 7 OUVCG I ML-3 -wTRANSFER CONTROL MEANS 5 FIG. 3

to AC Power Source 2 STANDBY POWER SOURCE FOR AN AC ALARM SYSTEM Thisinvention pertains to standby power sources and more particularly tosuch sources for supplying an alarm system.

Many local fire alarm systems used in schools, hospitals and the likeare AC systems wherein the components such as bells, sensors andmagnetic door releases rely on AC power.

Lately because of the prevalence of power failures, brownouts and thelike, it has become apparent that reliably operating AC alarm systemsrequire a standby source of power. In fact, some states now require suchstandby sources in schools and similar institutions. Accordingly, manyusers are adding motor-generator sets to supply the standby power. Whilesuch sets can perform this function they have several drawbacks. Thesets incorporate internal combustion engines which utilize gasoline orother hydrocarbons as their fuel source. Therefore, not only are theproblems associated with the storage of such combustible fluids presentbut also there are pollution problems associated with the fumesproducted by the internal combustion engines. Furthermore, because ofthe inertia in such generators, there is a lapse in time from the timethe generator is signaled, generally by the sensing of a power failure,and the time the generator delivers its rated output. Accordingly, it ispossible for the system to transmit a false alarm due to relays droppingout during the time lapse.

It is accordingly a general object of the invention to provide animproved standby power source for AC alarm systems.

It is another object of the system to provide such a power source whichdoes not have the problems associated with motor-generator sets.

It is a further object of the invention to provide such a power sourcewhich while satisfying the abovementioned objects is compact andrequires a minimum of service, repair and maintenance.

Briefly, the invention contemplates apparatus connected to AC powermains for supplying power to an AC alarm system when there is a failureof power from the AC power mains. The apparatus comprises a source of DCpower and inverter means for converting DC power to AC power. There is afirst switching means for connecting the source of DC power to theinverter means, and a second switching means for transferring theconnection of the AC alarm system from the AC power mains to theinverter means. The switching means are activated when there is afailure of power from the AC power mains.

Other objects, the features and advantages of'the invention will beapparent from the following detailed description when read with theaccompanying drawing which shows, by way of example, and not limitationa presently preferred embodiment of the invention.

In the drawing:

FIG. 1 is a block diagram of an AC alarm system supply includinginverter 7, battery 8 and battery charger 9 under the control oftransfer control means 5.

The operation of the apparatus is such that as long as source 4 deliversAC power, AC alarm system 6 receives its power from source 4 and batterycharger 9 receives power from source 4 to trickle-charge battery 8. Whenthere is a failure of power from source 4, transfer control means 5senses such failure and switches the connection of AC alarm system 6from source 4 to the output of inverter means 7. At the same timetransfer control means 5 causes the actuation of inverter means 7 anddisconnects battery charger 9 from battery 8 to prevent a needles drainon the battery. Then DC power accumulated in battery 8 is converted toAC power by inverter means 7 to power the AC alarm system 6 until thepower failure is corrected.

When AC power is restored and its restoration sensed by transfer controlmeans 5, AC power source 4 is reconnected to AC alarm system 6 andinverter means 7 deactivated under the control of transfer control means5. Simultaneously battery charger 9 is reconnected to battery 8 to fastcharge the latter to full charge and thereafter furnish a tricklecharge.

The elements of the apparatus will now be described.

AS power source 4 is the conventional public utility lines furnishing atterminals A and 110 B two different phases of AC power with respect toneutral terminal N.

AC alarm system 6 can be a conventional fire alarm system or the likehaving bells, gongs, door release devices, etc., all operated by ACpower received at its terminals 110. The neutral of the system isconnected to neutral terminal N and, via a line, to a similar neutralterminal N of power source 4.

Battery 8 can be a conventional array of rechargeable wet cells having apositive output terminal and a negative output terminal Battery charger9 can be a conventional battery charger which includes rectifiers andregulators for converting AC power received at its input terminals 110 Band N to a DC current which is delivered to its output terminals andInverter means 7 which can take many forms converts DC power received atits input terminals and from battery 8 to 60-cycle AC power deliveredfrom its output terminals 110 and N when transfer control means 5 closesa path between the control terminals T1 and T2. A preferred invertermeans 7. is shown in FIG. 2 comprising relay Rl'whichcontrols theenergization of transistor oscillator circuit OSC having an outputtransformerT. The oscillator circuit is suchjthat when a DC voltage isapplied across its input terminals it immediately breaks'intooscillation. The circuit can be of the master-oscillator power-amplifiertype or power oscillator type which generates 60-cycle sinusoids, or ofthe free-running relaxation oscillator generating square waves whichdrives a tuned power amplifier for convering the square waves toessentially sinusoids. When transistors are used as the active elementsof the oscillator circuit the input terminals thereof are effectivelyconnected across the emitter-collector circuits of the transistors sothat the DC power from battery 8 provides the operating power for theoscillators and amplifiers.

The transfer control means 5 is shown in FIG. 3 centered around tworelays R2 and R3. The coils L2 and L3 of relays R2 and R3 arerespectively connected across terminals 11 and 12 to receive alternatingcur rent from AC power source 4. When such current is present the relaysare energized with their contacts in the positions shown in FIG. 3.Associated with relay R2 are two sets of contacts 1K2. and 2K2. Themovable contact of set 1K2 is connected via terminal 13 to the terminalof battery charger 9 (see FIG. 1) while the fixed contact is connectedvia terminal 14 to the terminal of battery 8. The movable contact of set2K2 is connected via terminal 16 to terminal T2 of inverter means 7,while the fixed contact is connected via terminal 15 to terminal T1 ofinverter means 7.

Relay R3 has two contact sets 1K3 and 2K3. The upper fixed contact ofset 2K3 is connected via terminal 17 to output 110 of inverter means 7(see FIG. 1) as is the upper fixed contact of set 1K3. The movablecontact of set 2K3 is connected via terminal 18 to one input 110 ofalarm system 6 while the movable contact of set 1K3 is connected viaterminal 19 to the other input 110 of the alarm system 6. The lowerfixed contact of set 2K3 is connected via terminal 11 to output 110 B ofAC power source 4 while lower fixed contact of set 1K3 is connected viaterminal 20 .to output 110 A of AC power source 4.

The operation of the apparatus will now be described. When AC powersource 4 is operating alternating current is applied through terminals11 and 12 energizing relays R2 and R3 of transfer control means (FIG. 1and 3). Contact Set 1K2 connects terminals 13 and 14 connecting theterminal of battery charger 9 to the terminal of battery 8. Therefore,charger 9 is operatively connected to battery 8 and since charger 9 isreceiving AC power from AC power source 4, battery 8 is being charged.Since contact set 2K2 is open inverter means 7 is not activated as willhereinafter become apparent. The contact set 2K3 connects terminal 18 toterminal 11, connecting terminal 110 B of AC power source 4 to one ofthe terminals 110 of AC alarm system 6. The contact set 1K3 connectsterminal 19 to terminal 20, connecting terminal 110 A of source 4 to theother terminal 110 of alarm system 6. Therefore, AC alarm systemreceives its power from AC power source 4.

When AC power source 4 fails relays R2 and R3 drop out. The connectionbetween terminals 13 and 14 opens, disconnecting battery charger 9 frombattery 8. Contact set 2K2 closes connecting terminals 13 and 14 whichconnect terminal T1 to terminal T2 of inverter means 7. The shorting ofterminals T1 and T2 connect the coil of relay R1 across terminals and ofbattery 8 (see FIG. 2). Relay R1 is energized and its con- 4. tact setcloses connecting terminals and of battery 8 to the inputs of transistoroscil-lator circuit OSC. Circuit OSC starts oscillating and deliverssixty cycle alternating current at the terminals and N of the invertermeans 7. a

At the same time the contact sets 1K3 and 2K3 of relay R3 (FIG. 3)transfer. Terminal 17 is connected to terminal 18 and to terminal 19.Therefore, terminal 110 of inverter means 7 is connected to bothterminals 110 of AC alarm system 6 and alarm system 6 is powered byinverter means 7. The situation remains in this state until ACpower-source 4 again delivers power. At that time the system returns toits initially described state.

It should be noted that by using transistorized oscilla tors in invertermeans 7 the delivery of standby power is almost instantaneous preventingthe possibility of false alarm generation.

What 'is claimed is:

1. Apparatus for supplying AC power to an AC load comprising AC inputmeans for receiving AC power from AC power mains, a battery, a batterycharger having an input connected to said AC input means and an output,a battery having terminals, an inverter means for converting DC power toAC power and having an input for receiving DC power and an output fortransmitting AC power, said inverter means including a solid stateoscillator means which is energized to generate AC power upon thereceipt of DC power, a first con trolled switching means normallyconnecting said AC input means to the AC load, and when switched openingsuch connection a second controlled switching means normally connectedthe output of said battery charger to the terminals of said battery andwhen switched opening such connection, a third controlled switchingmeans which is normally open and when switched connecting the terminalsof said battery to the input of said inverter means for energizing saidsolid state oscillator means, fourth controlled switching means which isnormally open and when switched connecting the output of said invertermeans to the AC load, and control means connected to said AC input meansand operative in the absence of AC power on the AC power mains forswitching each of said switching means.

2. The apparatus of claim 1 wherein said control means is the windingmeans of a relay means and each of said controlled switching means is acontact means of said relay means.

1. Apparatus for supplying AC power to an AC load comprising AC inputmeans for receiving AC power from AC power mains, a battery, a batterycharger having an input connected to said AC input means and an output,a battery having terminals, an inverter means for converting DC power toAC power and having an input for receiving DC power and an output fortransmitting AC power, said inverter means including a solid stateoscillator means which is energized to generate AC power upon thereceipt of DC power, a first controlled switching means normallyconnecting saiD AC input means to the AC load, and when switched openingsuch connection a second controlled switching means normally connectedthe output of said battery charger to the terminals of said battery andwhen switched opening such connection, a third controlled switchingmeans which is normally open and when switched connecting the terminalsof said battery to the input of said inverter means for energizing saidsolid state oscillator means, fourth controlled switching means which isnormally open and when switched connecting the output of said invertermeans to the AC load, and control means connected to said AC input meansand operative in the absence of AC power on the AC power mains forswitching each of said switching means.
 2. The apparatus of claim 1wherein said control means is the winding means of a relay means andeach of said controlled switching means is a contact means of said relaymeans.